The present invention relates generally to a remotely reading means for determining the angular orientation, speed and/or direction of rotary objects such as shaft, dial or meter hands, counter wheel of cyclometer, and the like. More particularly, this invention is concerned with electrically obtaining a signal that is indicative of the angular orientation, speed and/or direction of rotary objects to be monitored without altering the accuracy and operation of the conventional utility meters or the like.
In electric utility system, for instance, sufficient power-generating equipment must be provided at all time to supply power during relatively short period of maximum consumption, however much of this equipment otherwise remains idle for major portion of each day. In order to discourage high power consumption during maximum-demand periods by graduated billing rates, or even to disconnect non-essential portions of customer's load when the customer exceeds a previously agreed consumption rate compatible with the optimum generation capacity of the utility company, rapid determination of an individual customer's consumption rate, commonly termed "demand" over a prescribed time interval is necessary.
Heretofore, such demand metering has generally been possible only through the use of specially equipped meters, commonly limited to a fixed time interval and not capable of transmitting information upon demand to a load-monitoring station in time for the station to take corrective action. There has been considerable effort expended in providing means and apparatus for reading meters at a distance, for example, through telephone lines and the like.
There may be four categories in remote meter reading means: photoelectric cell; sliding mechanical contact; magnetic field; and electric field.
The photoelectric cells have been used in meter reading devices, so that no mechanical connection is needed between the meter and the meter reader. However, these reading devices have been unsatisfactory because a reliable source of light must be provided and the face of the photoelectric cell must be kept sufficiently clean so that the light impinging on the photoelectric cell will not be diminished sufficiently to give a false reading.
The sliding mechanical contact sensor has been used in Neptune's remote meter reading systems granted the U.S. Pat. No. 3,614,774. The use of such sensor is prevented in explosive atmospheres, and in certain instants, changes in the output signal have been noted due to the aging of the components which can change its mechanical and/or electrical characteristics. This type of sensor can not be used for meters which must have high sensitivity such as Watthour meters, because its high pressure on contact.
Magnetically induced reading system was invented by Cain who obtained the U.S. Pat. No. 3,500,365. on it. Cain invented an improved electrically induced reading system by using an electrical transducer unit instead of the magnetic coupling and obtained the U.S. Pat. No. 4,007,454 and U.S. Pat. No. 4,429,308 on it. This sensor has high resolution because the phase of the output signal of the sensor is detected to determine the angular orientation, speed and/or direction of rotary objects. In order to easily detect the phase of the output signal, high frequency input signal has to be used, and therefore, the circuit accompanying the sensor becomes complicated and expensive.
Capacitively sensing device for remotely determining the angular orientation, speed and/or direction of rotary objects was invented by the inventors of this invention and was filed at the Office of Patents Administration of Korea on Apr. 15, 1985. The output signal of the capacitive sensor is in proportion to the capacitance between a stationary electrode and a rotary electrode. The rotary electrode has a physical coupling means to electronic circuit which can be provided at a low price.
However, the capacitively sensing device also has the limitation in the application to the rotary objects with very high speed or small size.
There is thus a need to provide an improved apparatus for determining the angular orientation, speed and/or direction of rotary objects without physically connecting the rotary objects to the measuring device.
Moreover, there is a need to provide an apparatus having an improved characteristics so as to apply it to a rotary objects with small size.
It is accordingly an object of the present invention to provide the capacitively sensing device having improved characteristics and the capacitively reading apparatus which consists of said capacitively sensing device and circuit being manufactured at a very low price, for automatically reading the indication of counter wheel or of pointer of the conventional utility meters such as Water meters. Gas meters, and the like, without affecting the accuracy and operation of the conventional utility meters.
It is another object of the invention to provide a capacitively reading apparatus with improved resolution so as to remotely read the angular position of a rotary objects with small size.
With the apparatus being described herein, any utility meters which are mechanical register type or pointer type can be read by the load-monitoring station with extreme speed permitting the reading of many meters during a short time period, as well as taking several sample readings from each meter to increase the statistical validity of the readings. Thus the utility company can determine not only the total energy consumed by any individual customer during a normal billing period, but also can monitor his demand rate during any desired time interval.